Automatic steering system



Oct. 14, 1952 T. T. EATON 2,614,249

AUTOMATIC STEERING SYSTEM Filed oct. 9, 1946 2 SHEETS- SHEET 1 Ai D f! d new;

F7' rff f" I' a. aww/www@ j AMEN/YA j A/Yre'N/YA Pas/mw 2 7 Zi Oct. 14, 1952 T. T. EATON AUTOMATIC STEERING SYSTEM 2 SHEETS- SHEET 2 Filed Oct. 9, 1946 I N V EN TOR. 72mm.; Tinian BY A QQ l Afro/@Vey Patented Oct. 14, 1952 UNITED sfr-Ares ATENT GFFICE l "nnrom'riosme SYSTEM Y :Thomas fr. Eatomnadam Heights, N. J., assigner vv'toRarilio Corporation of America, a corporation Application October `'9, 1946; Serial No. 702,109

inventionirelates to fgiudingnsystems Awhich are fadapted rito steer aamovingfvehicle automatically fto a l desired harbor which .may `be .stationarylorrmayrbeinthe former another moving vehicle such'was fan :aircraft .or lthe l like.

`:Various `types of irautomatic guiding systems have been'lprovidedin the pastffor automatically steeringa-water borne Avehicle into a stationary harbor. `Similar types yof: guiding systems YVhave vbeen provided for automatically steering a bomb lorrmissile into contact with a moving "aircraft,

The 'guiding propulsionlsystem of the 4present invention ist distinguished from such prior systemsbyithesfact that its operation is controlled byltanla'lternatingrpotentiallhavng a frequency y. which .ds th'e resultant ndifference .between the frequencys'of .aradio .wave transmitted from `the moving Avehicle to Ithefharbor 'or target and the l frequency `ofthal-partof such `radio wave as is reflected `lcanktfrom the harbor or targetito the movingvehicle.

l `the case *where a radio transmitter :and l a radio 4receiver are zmounted on :a moving vehicle, itiszwellrknown `that the frequencyof the wave emittedlby the transmitter is diiferent from `the frequency 4of. that part `of l the `Vwave vwhich is reiectedsrfrom `an externalobject back to rthefrelceiver. `:Such frequency `difference (sometimes termed the Doppler shift) for the velocities n-Y volved isi-proportional to `thespeed of the vehicle withrrespect to thenharbor or target. Thus the received zsignal hasla Vfrequenoywhich 'is relatively fhigh Vwhen the 'vessel is approaching the harborsor target and is relatively Alow when the vehicle is receding from the harbor or target.

ltwisievident that this frequency shift will be )greatest when the course; of :the `moving vehicle y is on `a line which intersects the harbor or target. Therefore in order to make the -vehcle followahoming course, it is necessaryto direct it so that the frequency shift is a maximum.

`'in flaconi-dance with the present invention, this it isassumed for the purpose of illustration that the transmitting antenna is rotated about an axis'parallel to the longitudinal axis of the4 moving vehicle.

Important objects of the invention are the provision of an improved `vehicle guiding system and method of operation, the Vprovision of an improved system whereby a homing missile 'is caused to follow a course which eventually intersects `a moving object, and the provision of a vehicleguiding system which responds to the frequen'cy shift between a transmitted signal anda reflected signal to control the course of the vehicle so that it reaches the object from which the transmitted signal is reflected.

The invention will be better understood from the following description considered in connection with the accompanying drawings and its scope is indicated by the appended claims.

Referring to the drawings:

Figure 1 is a diagrammatic showing of a moving vehicle `zr from which a radio signal isVv transmitted to an object b which reflects a part of such signal back to the vehicle a,

FigureZ is .an explanatory diagram relating'to the velocity components involved in the relation between the vehicle a and the object?) of Figure'l;

Figure 3 illustrates a moving vehicle having its transmitting antenna arranged to rotate about an axis which is parallel with the longitudinal axis of the vehicle,

Figures 3c,`3b, 3c and 4 are explanatorydiagrams relating tothe operation of thevehicle of Figure '3,

Figure 5 is a box diagram of the improved propulsion system, and

Figure 6 is a wiring diagram of that part of Figure 5 which is Vdesignated fas iControl Circuits. Y

Figure l shows a moving vehicle a upongwhich aremounted an antenna `Hl which emits av continuous wave signal Il and anantenna .12v/hielo receives that part I3 of the signal -lwhich is reflected from -an objec'tb `which -lnayfbe aY-stationary reflector or a movingvehiclesuh -as an aircraft. i

As previously indicated'the frequency offthe received signal diners from `that of itheltrarrlsmittedlsignal by a` value which is dependent/on the relative motion betweenthe vehicle-mand the object b. This frequency ldifierenee *is proportional tothe componentuof velocity alon'g a straight line between-the lvehicleV and the `signal reflecting object. 'If-*the vehicle yandfoofject move with 'constant speed,` the `component of velocit',-Y

along this line (see Figure 2) will be a maximum when the vehicle is moving directlyV toward the object. Therefore, the vehicle d can be directed to the object bI by adjusting its direction of night so that the frequency of the received signal is maintained at its maximum value. Y

vIn order to determine if the received signal is at its maximum value, itis necessary to compare the frequency of the signal actually received with i the frequency of the signal which would be iov received if the vehicle were proceeding on av course above, below, to the right or to the left of the straight line between the vehicle and Y reflecting object. The direction of` the movement of the vehicle could be changed to provide this information but this would require consider- -able power and 'a complicated control mechanism. A much simpler way yof derivingv this information is by rotation of the transmitting antenna Il] as indicated by Figure 3.

The effect of such rotation of the transmitting antenna I about an'axis parallel vto the longitudinal axis of the vehicle a is shown by Figures 3a, 3b and 4.

In Figures 3a and 3b, the vector I4 represents the motion of the vehicle a, the vector I5 represents the motion of the antenna I0 with respect to the vehicle and the vector I6 represents the resultant of the two motions.

Thus when lthe antenna I0 is at the top of its circular path (with its direction of rotation as indicated by the arrow) the resultant motion is to the right of the straight line between the vehicle and reflecting object as indicated bythe vectork I6 of the Figure 3a. Likewisewhen the antenna is at the bottom of its circular path, the resultant motion isto the left of this straight `line as indicated by the phase of the wave indicates the direction of the error. s

This information is converted into a usable form by the apparatus of'Figure 5. This apparatus includes a transmitter Il from which a continuous waver radio signal is transmitted (1) 'through the antennal to the reflecting object b, and (2) through a lead L8 toamix'er and lter I9. In the device-I9, the signal frfrom the transmitter I'Il isheterodyned with a signal .fLo from a= local oscillator 20 to produce an intermediate frequency-signal fis-fro which is fed to a de- Alsov fed to the detector 2I is the through whichpcertain circuit control camsv (described in connection with Fig. 6) 'are' operated in synchronisin with rotation of thev antenna. These various circuit\elements are for the most p part of conventional form and easilyv understood without detailed consideration. The connections of the control circuits 24 and those by means of which the antenna positionrepresentative pothe vector IB of Figure 3b. In between these positions, the vector I5 (representing the movement of the antenna I0 with respect to the vehicle a) rotates about the end of the vector I4 which represents the movement of the vehicle.r

In this way is produced a scanning eifect'similar to that of the well known conical scan radar with, the exception that in this instance the velocity of the vessel is scanned instead of the direction of a radio beam.

Itis evident that if the vehicle is moving directly toward the .reflecting object, the rotation of the antenna III will not aiect the frequency of the received signal and no control effect will be exerted on the'steering elements ofthe vehicle; This is so for the reason that the length of the resultant vector I6 (Figure 3a and Figure 3b) varies only with change in the velocity of the vehicle. If the vehicle is moving to the right of its direct course ab, for aA given direction of antenna rotation and-relative motion of (a) and (b), the frequency of the received signal will be less When the antenna (a) is at the top of its circular path than when it is at the bottom of this path. This follows from the fact that the movement of the antenna I0 with respect to (b) (see Figure 3c) is greatest in the direction away from (b) when the antenna is at the top of its travel. Similar considerations apply when the vehicle Vis moving from its direct path in other directions not too far away from the direction of the reflecting object.

The frequencyof the signal received when the course of the vehicle is to the right of the reflecting object is indicated by Figure 4. Here the amplitude of the wave provides a measure of how far the vehicle is off its direct course and vvte'ntial isderived are shown in Figure 6 hereinafter described." n It is desirable that `the transmittery I1 have very good'frequency stability for times `of theorder of the rotational'pe'riod of the antennaxl and that the frequency stability of the local oscillator 2Q also be good. The lower sidefrequency of the heter'odyned signal ftlgfm is filtered 'out in the device I91and is mixed with the received signal ffr-l-Af in the first detector'Z I It is evident that the variations in the transmitter'frequency are cancelled out under these conditions so that kthe band width of the intermediate frequency amplifier 22 need be only wide enough to accommodate the frequency shift Af together with vari-` I ationsgin the frequency of the'local oscillator 20.

. Whichindicates how` far the vehicle a is :off-'itsv Course.

fIn order that the amplitude of the output potential of the second detector be truly representa'- Vtive ofthe frequency shift Af, it is necessary that the output voltage of the intermediate frequency amplifier 22 be heldconstant. This can be done either by means of an automatic volumecontrol or with'afclipper as is Icustomary frequency modulation= receivers: The output of thefsecondi-de-L tector is a sinusoid. having. (l)r anfar'nplitude direct :course and (2) a `phase which is constant so long as vthe'ive'ssel a is on its true cours'eibut shifts in a direction dependenton the' course of the Vessel 'a when: thisftravell d is off its true This sinusoid is utilized-to operate the controls ofthevehicle in; a manner' to constantly return it to its direct course.`

i The details of the control circuits'areindicated by'Figure 6. y e c The mechanism for rotating the? transmitting antenna I may'assume 'variousiforms VIt is shown as mounted at one end of an arm `255 which may have a counterweight atiits oppositee'nd and is arranged to rotatewith'a shaft 2'I'fdriven Kbya motor 28.-y f

Also driven by the motorgf28fare aplurality of cam controlled switchesj', 3d, jand 3'! which connect the output lead of the discriminator4 and detector 23 (Figure 5) successively to theurigrounded terminals of the ycapacitorsgy 4I, 39 and 42 vso that the charges*,ofi-.hiessf capacitors fer-enceibetween the.A transmitted.

agata-'24a nais# when* theL antenna is-a't its top;- bottom, left andri'ght positions. '-I-hus'when' the:u antenna- I IJ isinits top` or1U*position-, the switch 33- is closed so that" the output potential of Z3-is applied to to the object-17"; the-capacitors@ yand 39 are maintainedf-attlie same voltage so that they produce no-resultantfvoltageat their output-leads; These'v leads-are-` interconnected` throughv aresistor M',

theprimaryA I8? of a transformer E9- and a cam f swfi'f'zl'r li'f` which is--rotatedby the motor 28 to clseethe-primary circuit 48; at-a time when the switchesf and-34 are open. When the vehicle ae-iSi-oits-*direct' course, however thereV is proi` duced" a resultant voltage' which is applied through the `secondary"winding 5ll andl an amplifier 52- tol a motor 5B by which theelevation controlffoftlie--vehicle is" operated to return the"vehiclefto its-direct-course.

The-train controlofthe vehicle a issimilar to its-*elevation control and opera-tes in the same way-toreturn the `vehicle to itsv direct course when atresultantpotential other than zero is applied through the switch 61, the transformer (ity and thelamplifler B2i-4to the train-amplier 68 to the train-icontrol-motor 111,

An important feature of the invention is the provision of means-for utilizing 'the-frequency difand received signals to detect slight deviations-ofthevehicle from its direct-zcourseandto immediately exert a force by which such deviation is corrected.

l claim-f as my invention:

l. In-combination, radar apparatus comprising an antenna-- system that comprisesv at least one antenna having a directivelradiation pattern that has `a principal axis, said antenna system being mounted oli-means` for pointing said axisof said one* antenna toward a reectingV target, means for-'repetitively changing the eiective position' of said-one antennain a direction having acomd pene'nt transverse to said principal axis, means for-f radiating a-radio signa-l from said antenna system during the time that said one antenna is changing from one effective position to another effective position, means for receiving said signal by said antenna system after reflection from said target, means for obtaining a Doppler frequency signal resulting from relative motion of said target and said one antenna, said last means comprising a detector, means for supplying a frequency comparison signal to said detector and means for supplying said received signal to said Hdetector, whereby there is obtained a Doppler frequencysignal that varies repetitively in frequency as a function of said repetitive change in the effective position of said one antenna so long as said principal axis is not pointing directly toward said target.

2. In combination, radar apparatus comprising an antenna system that comprises at least one antenna having a directive radiation pattern that has a principal axis, said antenna system being mounted on means for pointing said axis of said `one antenna toward a reflecting target, means for repetitively moving said one antenna in a direction having a component transverse to said principal axis, means for radiating a radio signal from sadantenna system While said one antenna islmoving; means-frreceiving-said:signal by-fsaidantenna system after. reflection'- from'- said target',r` means-forobtaining al Doppler frequency signal4 resulting from relative" motion ofsaid-target and. said one antennai said last meansvcomprising adetector, meanslforsupplying avfrequenc'y com-- parisonsignal to= said detector and meansfor supplying said receivedsignal to said'` detector; whereby there is'- obtainedI a Doppler frequency` signal that varies repetitivelyfinl frequency asi a function-of saidrepetitive-motion-of' saidi one antennaso long assaid principal axis is noti pointing-directly toward saidtarget.

3J In'combi-na'ticn', radar apparatus comprising` an* antenna systemthat comprisesat least '-oneantennahavinga'directive. radiation patternftliat has a-principal axis; said antenna system being' mounted on means forpointing said'axis of` said'- one antenna toward areflecting target, an4 armrota-table about a pivot' point, said one antenna being mounted on one end ofsaid arm remote from said pivot point,Y means for spinning saidarm and thereby moving. said one antennain a direction having'` a component transverseto said` principal axi'swhile said one antenna is moving,

means for radiating a radio signal from` said antenna system, means-for receiving said signal bysaid antenna-system after reflection fromsaidtarget, means for obtaining a Doppler frequency' signal resulting from relative motion of said tar-- getand said one antenna, saidl'ast means-com-V prising adetector, means for supplying' a fre-fv quency comparison signal to said detectorV and means-for supplying` said received signal to' said'- detector, whereby there is obtained a- Doppler frequency signal that-varies repetitively in fre quency as a function of the repetitive change in the position of said one antenna so long as said principal axis isxnotpointing directly toward saidtarget.

4. In combination', radar apparatus comprising an antenna system that comprises at least-one antenna having a directive radiation pattern that has a-p-rincipal axis, said antenna system being mounted on means for pointing said axis of said one antenna toward a reecting target, means for repetitively changing the effective positionof said one antenna in a direction having a component transverse to said principal axis, means for radiating aradio signal from said antenna` system during the time that said one antenna is changing from one effective position to another eiective position, means for receiving said signal by said antenna system after reflection from said target, means for obtaining a Doppler frequency signal resulting from relative motion of said target and said one antenna, said last means comprising a detector, means for supplying a frequency comparison signal to said detector and means for supplying said received signal to said detector, whereby there is obtained a Doppler frequency signal that varies repetitively in frequency as a function of said repetitive change in the eective position of said one antenna so long as said principal axis is not pointing directly toward said target, and means for converting said Doppler frequency signal into control signals, and means for moving said antenna system as a function of said control signals to point said principal axis toward said target.

5. Radar apparatus for guiding a steerable device toward a target comprising in combination, an antenna system that comprises at least one antenna having a directive radiation pattern that has a principal axis, said antenna system being mounted Von saidysteerable device-,whereby said axis of said-one antenna may be pointed toward said target by steering said devicetovvard said target, means for repetitively changing the eiective position -of said one antenna in a direction'A having a component transverse to said principal axis, means for radiating a radio signal from said.

antenna system during the time that said rone antenna is changing from one eiective position to another effective position, means for receiving said signal by said antenna systemy after reflection from said target, means for obtaining a Doppler frequency signal resulting from relative motionof said target and saidv one antenna, said last means comprising a detector, means for supplying a frequency comparison signal to said 'defytector and means for supplying said received signal to said detector, whereby there is obtained Va Dopplerfreqnency signal that varies repetitively in frequency asv afunction of said repetitive changein the effective position of said one andirectly toward said target, and means for controlling the direction of travel of said steerable device as a function oi` said Doppler frequency signal.

v6. In combination, radar apparatus comprisingy an antenna system that comprises at least one antenna having a directive radiation pattern that has a principal axis, said antenna system being mounted on means for pointing said axis of said one antenna toward a reflecting target,means for repetitively changngthe effective position of saidv one antenna in a direction having'a component transverse to said principal axis, means for radi-v ating a radio signal from vsaid antenna system, means for receiving said signal by said antenna system after reflection from said target, means for obtaining a Doppler frequency signal resultv ing from relative motion of said target and said `one antenna, said last means comprising a detector, means for supplying a frequency comparison signal to said detector and means for supplying lsaid received signal to said detector, whereby there is obtained a Doppler frequency signal that varies repetitivelyin frequency as a function or"V said repetitive change in the eiective position of said one antenna so long as said principal axis is not pointing directly toward said target, a frey quency discriminatcr and a second detector tenna so longk as said principal axis is not pointing Y through which said Doppler frequency signal is passed toobtain a periodic Wave having an amplitude that is a function of the angle of said principal axis with respect to a direct line to said target and having a' phase that-reverses in response tosaid principal axis moving from one side of said direct linevto the opposite side of said direct line. i'

7. A radar system mounted on a steerable device that isl tomove towardga reecting object,

said system comprising an antenna system ,for

transmission and K4 .receizitioia, said antenna system comprising at least one antenna, means for transmitting airadio. Wave -from said antenna system,

toward saidy reflecting object, means for repeti-` tively changingthe effective position ofl'ksaid antenna in a direction having a component transverse to the` line of motion of said device, means v for receiving the-.radio Wave reflected from said object, receiving means to which the received wave is supplied, said receiving means Vincluding means.r Vfor heterodyning the received wave to obtain the Doppler frequency signal resulting from relative motion of said one antenna and said reecting object, and a frequency discriminator and y detector through which said Doppler frequency signal is passed to obtain a periodic wave having ari-amplitude V thatis a function of theamount of departure'frcnithe course directly toward said object and having` av phase that is a function of l the direction ofideparture from said direct course.

THOMAS T. EATON... i insertan'Nens CITED The following references are of record inthe A file of this patent:v I

UNITED sTA'rEsPA'I'ENTs l Rost et a1 oct. 11, l1949 

